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| author | Dan Williams <dan.j.williams@intel.com> | 2010-10-13 15:43:10 -0700 |
|---|---|---|
| committer | Dan Williams <dan.j.williams@intel.com> | 2010-10-13 15:43:10 -0700 |
| commit | c50a898fd4e736623ee175920db056194e0bb483 (patch) | |
| tree | 271750360d57da1d982686d8435b8eb3bf3086e4 /drivers | |
| parent | cc60f8878eab892c03d06b10f389232b9b66bd83 (diff) | |
| download | lwn-c50a898fd4e736623ee175920db056194e0bb483.tar.gz lwn-c50a898fd4e736623ee175920db056194e0bb483.zip | |
ioat2: fix performance regression
Commit 0793448 "DMAENGINE: generic channel status v2" changed the interface for
how dma channel progress is retrieved. It inadvertently exported an internal
helper function ioat_tx_status() instead of ioat_dma_tx_status(). The latter
polls the hardware to get the latest completion state, while the helper just
evaluates the current state without touching hardware. The effect is that we
end up waiting for completion timeouts or descriptor allocation errors before
the completion state is updated.
iperf (before fix):
[SUM] 0.0-41.3 sec 364 MBytes 73.9 Mbits/sec
iperf (after fix):
[SUM] 0.0- 4.5 sec 499 MBytes 940 Mbits/sec
This is a regression starting with 2.6.35.
Cc: <stable@kernel.org>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Jesse Brandeburg <jesse.brandeburg@intel.com>
Cc: Linus Walleij <linus.walleij@stericsson.com>
Cc: Maciej Sosnowski <maciej.sosnowski@intel.com>
Reported-by: Richard Scobie <richard@sauce.co.nz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/dma/ioat/dma_v2.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/dma/ioat/dma_v2.c b/drivers/dma/ioat/dma_v2.c index 216f9d383b5b..effd140fc042 100644 --- a/drivers/dma/ioat/dma_v2.c +++ b/drivers/dma/ioat/dma_v2.c @@ -879,7 +879,7 @@ int __devinit ioat2_dma_probe(struct ioatdma_device *device, int dca) dma->device_issue_pending = ioat2_issue_pending; dma->device_alloc_chan_resources = ioat2_alloc_chan_resources; dma->device_free_chan_resources = ioat2_free_chan_resources; - dma->device_tx_status = ioat_tx_status; + dma->device_tx_status = ioat_dma_tx_status; err = ioat_probe(device); if (err) |